Well, gatling has 4 weaknesses that you should exploit.
1) It is very heavy weight when loaded that gives HUGE malus to weapon drops rolls, aim arms if you have aimable weapon.
2) It is walk only, use ground fire or choose position with cover if possible. Gatling is best against immobile targets in open space such as deployed MG, so remember it.
3) Gatling deals more and more DPS as it shoots you. After first shot it has 800 delay, after second 700 and after third 600, and so on up to 400, so do not let it focus fire on you for longer than few shots. Rate of fire bonus resets afte 3 seconds. Be mobile, use hard/soft cover.
Also comparing Gatling and MMG you should remember that gatling is a single target weapon while MG's are area weapons.
Current gatilng is same as it was pre-wipe with exception that now it has 4.4% more base damage, so I do not get what do you mean saying "nominal" range.